The film opens with a bird's-eye sweep over the frieze of a post-engagement battlefield--mud, strewn with bodies and shards of machinery, all iron grey and relieved only by rare patches of crimson blood. Psychiatrist William Rivers (Jonathan Pryce) treats shell-shocked soldiers in the converted Craiglockhart Manor. He is obliged to admit the poet and decorated war hero, Siegfried Sassoon (James Wilby), because his military superiors prefer to label the much-loved Sassoon's public criticism of the war as insanity rather than treason. Rivers is supposed to "cure" the very sane poet of his anti-war sentiments.

At the hospital, Sassoon meets another poet, Wilfred Owen (Stuart Bunce), equally horrified by the war although he, like Sassoon, believes himself not to be a pacifist. A secondary plot is devoted to the mute officer Billy Pryor (Jonny Lee Miller) who recovers his speech, his memories, and a small portion of his self-respect through the patience of his doctor and his lover, Sarah (Tanya Allen). Vignettes of other personal horrors and the brutal psychological wounds they have caused are presented with riveting flashbacks to the ugly trenches. Sassoon, Owen, and Pryor return to active service. The film closes with a dismal scene of Owen's dead body lying in a trench.